During a selective hydrogenation process for unsaturated compounds, the raw materials may contain certain amounts of sulphides in addition to the unsaturated compounds, and all of the sulphides or portion of them are light sulphides. These light sulphides can react with polyunsaturated compounds in the raw materials under the action of a hydrogenation catalyst to generate heavy sulphides, which can be removed by a process of fractionation.
The polyunsaturated compounds in the raw materials as described above have very unstable properties and are easy to be polymerized during storage and subsequent processing. Under the action of the hydrogenation catalyst, a portion of the polyunsaturated compounds can be selectively hydrogenated into monounsaturated compounds.
At the time of hydrogenating the polyunsaturated compounds into monounsaturated compounds, a small portion of the polyunsaturated compounds or monounsaturated compounds are hydrogenated into saturated compounds, and the occurrence of such reaction can be avoided as much as possible by optimized design for the catalyst.
The methods of hydrogenation treatment for an unsaturated compound are proposed in the following patents or patent applications.
CN03815240.1 proposes a method for selective hydrogenation of polyunsaturated compounds into monounsaturated compounds using a homogeneous catalyst. This method uses at least one salt of a transition metal element from Groups IB, IIB, VB, VIB, VIIB and VIII of the periodic table, at least one ligand and at least one organometallic reducing agent.
CN200610064286.5 proposes a method of selective hydrogenation using a catalyst having controlled porosity. The method uses a catalyst on a carrier, comprising at least one metal from Group VIB and at least one non-noble metal from Group VIII used in the sulphurized form deposited on the carrier and having a controlled porosity, wherein: the weight content of Group VIB element oxide is necessarily higher than 12% by weight; the weight content of Group VIII element oxide is lower than 15% by weight; the sulphurization degree of metal components in the catalyst is at least equal to 60%; and the pore volume having a diameter larger than 0.05 microns in the catalyst is 10˜40% of total pore volume.
CN200610064287.x proposes a method for selective hydrogenation employing a sulphurized catalyst. The method uses a catalyst deposited on a carrier and comprising at least one metal from Group VIB and at least one non-noble metal from Group VIII, wherein: the weight content of Group VIB element oxide is necessarily higher than 12% by weight; the weight content of Group VIII element oxide is lower than 15% by weight; the sulphurization degree of metal components in the catalyst is at least equal to 60%; and the molar ratio of the non-noble metal from Group VIII to the metal from Group VIB is 0.2˜0.5 mole/mole.
CN200610064397.6 proposes a method of selective hydrogenation using a catalyst with a specific carrier. The method uses a supported catalyst comprising at least one metal from Group VIB and at least one non-noble metal from Group VIII used in the sulphurized form, deposited on a specific carrier comprising a metal aluminate of the MAl2O4 type with a metal M selected from nickel and cobalt.
CN200910170584.6 proposes a method for selective hydrogenation using a sulphurated catalyst with a specified composition. The catalyst comprises at least one metal from Group VIB and at least one non-noble metal from Group VIII supported on alumina, wherein: the Group VIB metal oxide is 4˜20% by weight of the catalyst; the Group VIII non-noble metal oxide is less than 15% by weight of the catalyst; the molar ratio of the non-noble metal from Group VIII to the metal from Group VIB is 0.6˜3.0 mole/mole; and the catalyst has a total pore volume of 0.4˜1.4 cm3/g.